Today I got a warning from the datacenter, telling that one of my server has been used for spamming. It threatened to disconnect my server is nothing is done about it.
And also there's a prospect that my server will be blacklisted by SpamCop, causing problem for everyone hosted in that machine.

OK, I thought this should be pretty easy to solve; years ago I was messing with OpenBSD 3.x as mailserver; and I think it's just changing a single setting in Amavis. But I couldn't remember which. Anyway, the "perfect server" howto doesn't use Amavis, so it had to be done in Postfix.

Let's recap: I want to disable ALL bounces.

With this in mind, I googled around. Unfortunately, everything I found was much more complex than I expected, and even then I doubt that it'd solve my problem WITHOUT the potential of causing more troubles.

I thought it'd be as simple as a single line setting in main.cf, such as "smtpd_recipient_restrictions = reject_unknown_recipient". But, there's no such setting.

The article at http://www.postfix.org/BACKSCATTER_README.html is useless too. Because it said "configure Postfix to reject all mail for non-existent recipients", but then the instructions are for local_maps; while the "perfect server" howto uses virtual_maps.

At the moment I've read numerous articles and still stuck.
Anyone got a hint on how to do this ? (disable all bounces)

However, instead of dropping the email; postfix will defer it. So the problematic emails will stay in queues.
Clearly I won't be able to use this setting for extended period. However, it helps to avoid being blacklisted by SpamCop for the time being

So I'll keep looking. If anyone knows a more permanent solution, please do share it with us as well.

Dear Harry,
I am facing similar problem on my system. Thanks for the tip to switch on the soft_bounce, it temporarily works for me as well. If you find more permanent solution, please post it here. I will do likewise.
Regards
Martin